1. Field of the Invention
The present invention relates to a method for manufacturing an optical element.
2. Description of Related Art
Glass is used in many optical elements. During the steps of manufacturing the optical elements, a processing liquid, foreign matter or the like may adhere to a surface of the glass to thereby contaminate the surface. Therefore, a cleaning step is appropriately performed on the glass so as to keep the glass clean. Further, in order to rinse out the cleaning liquid used in the cleaning step, a rinsing step is also provided together with the cleaning step.
Typically, pure water, other deionized water (hereinafter referred to as DI (Deionized) water), or the like as described in Patent Document 1 is used as the rinsing liquid used in this rinsing step.
On the other hand, as the polishing liquid, technology of making pH of the glass approximate to pH of a dispersion liquid which contains a polishing agent is disclosed in Patent Document 2. This technology is based on the idea of inhibiting a chemical reaction between the glass and the polishing liquid (refer to para. [0010] of Patent Document 2). Also in the cleaning liquid or the rinsing liquid, technology has been disclosed, which makes pH of the glass approximate to pH of the cleaning liquid or the rinsing liquid to suppress the occurrence of latent scratches (refer to para. [0021] of Patent Document 2). Here, a standard for determining the quality of glass is based on the presence or absence of linear scratches having the width of 7 μm.